Researchers have built a small chip that is implanted in the brain, where it measures a chemical messenger in real time and sends the results out wirelessly. The team was led KAIST, DGIST, the Korea Brain Research Institute, and the Korea Research Institute of Bioscience and Biotechnology.
The chip measures acetylcholine, a neurotransmitter, meaning a chemical that carries signals between nerve cells. Acetylcholine is important for memory and learning, and its levels fall in people with Alzheimer's disease. The drug donepezil slows the breakdown of acetylcholine, but it has been hard to see directly where in the brain, and for how long, such a drug acts.
The researchers implanted the chip in the prefrontal cortex of minipigs, a brain region involved in judgment, attention, and memory, and gave the animals donepezil. The acetylcholine signal rose, then slowly returned to its starting level, and the chip sent the measurements to an outside device by Bluetooth. Earlier studies of this kind mostly used rodents connected to wires.
This research is published in Device.
How the chip senses and stimulates
The sensing layer combines porous chitosan, a material full of tiny holes that offers a large surface for holding detection enzymes, with extremely thin silver and platinum nanowires. The enzymes react with acetylcholine and produce hydrogen peroxide, which the nanowires convert into electrical signals. To reduce false readings from other molecules, the probe carries an enzyme-coated electrode on one side and a bare electrode on the other, and the system compares the two signals.
The chip can also stimulate nerve cells with light from a built-in micro light-emitting diode. In a separate test in mice, this light stimulation raised acetylcholine signals, showing that a single chip can both trigger and record brain activity. That combination is a step toward closed-loop neural interfaces, devices that adjust their stimulation based on the brain's measured response.
For now, the results come only from animals and show no treatment benefit, so long-term safety and measurement stability must be proven before human use.